Suspension lower arm

Abstract

To provide a suspension lower arm capable of further improving rigidity and weight reduction with a simple configuration.SOLUTION: A first back plate material 8a for covering the entire main arm section 2 in a width direction is attached to a first portion closer to a center side of the main arm section from a wheel side attaching section 3 of the main arm section and the first portion has a box-shaped cross sectional shape. A second back plate material 8b for covering the entire of the main arm section in the width direction is attached to a second portion closer to the center side of the main arm section from a first vehicle body attaching section 4 of the main arm section and the second portion has a box-shaped cross sectional shape. A third back plate material 8c for covering the entire of a sub arm section 5 in the width direction is attached to at least a part of the sub arm section and at least a part has a box-shaped cross sectional shape. A support section 9 for connecting the first back plate material, the second back plate material, and the third back plate material is further provided.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a lower arm in a strut suspension. [Background technology]

[0002] A lower arm is a component of a strut-type suspension, and is provided between the vehicle body and the wheel, supporting the wheel from below so that it can move up and down. Patent Documents 1 and 2 describe examples of this type of lower arm, and both of these lower arms are what can be called L-shaped, with a gently curved L-shaped portion (hereinafter referred to as the main arm portion) having at both ends a ball joint attachment portion that is connected to the wheel and a first vehicle body attachment portion that is connected to the vehicle body in the vertical direction. A portion (hereinafter referred to as the sub-arm portion) branches off from near the middle of the main arm portion, and a second vehicle body attachment portion that is connected to the vehicle body in the horizontal direction is provided on the sub-arm portion.

[0003] Because the lower arm supports the wheel on the vehicle body, it must have high rigidity and be lightweight to allow the wheel to move up and down smoothly. The lower arm described in Patent Document 1 is configured with a box-shaped cross section by joining an upper arm and a lower arm that are nearly symmetrical in shape opposite each other, thereby achieving high rigidity and light weight. In addition, because the upper arm and the lower arm are joined by welding, the welding sequence is specified to prevent or suppress deformation due to welding.

[0004] Furthermore, the lower arm described in Patent Document 2 has a reinforcing portion provided in the section extending from the ball joint attachment portion through the sub-arm portion to the second vehicle body attachment portion. The main arm portion and the sub-arm portion have a concave cross-sectional shape with side walls provided by bending the side edges at right angles, and a reinforcing plate is joined to the tip of the side wall portion to form the reinforcing portion, with the cross-sectional shape of the reinforcing portion being box-shaped. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-73076 [Patent Document 2] International Publication No. 2015 / 151213 Summary of the Invention [Problem to be solved by the invention]

[0006] In the structure described in Patent Document 1, the entire structure is box-shaped, which allows for greater rigidity than a structure made of a single plate, and also allows for a lighter weight than a structure with the same rigidity. However, since the upper arm and lower arm are welded along the entire circumference where they come into contact with each other, this increases the number of work steps, increases the weight, and introduces many factors that lead to thermal deformation, leaving room for improvement.

[0007] Furthermore, the structure described in Patent Document 2 is intended to improve rigidity against loads from the left and right directions of the vehicle, and can improve the rigidity between the ball joint mounting portion and the sub-arm portion or second vehicle body mounting portion. However, since the lower arm is subjected to a variety of loads (bending loads and torsional loads), the structure does not necessarily satisfy the rigidity required of the lower arm, and there is still room for improvement.

[0008] The present invention has been made in light of the above technical problems, and aims to provide a suspension lower arm that can further improve rigidity and weight reduction with a simple configuration. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides a suspension lower arm, which includes a main arm section that is curved in an arc shape or an L shape and is provided with a wheel-side attachment section for attaching a ball joint at one end thereof, a first vehicle body attachment section for coupling to a vehicle body at the other end thereof, a sub-arm section that branches off from a portion of the main arm section between the wheel-side attachment section and the first vehicle body attachment section, and a second vehicle body attachment section for coupling to the vehicle body at a tip end thereof, wherein a first portion of the main arm section that is closer to the center of the main arm section from the wheel-side attachment section is provided with a second vehicle body attachment section for coupling to the vehicle body at a first location of the main arm section that is closer to the center of the main arm section than the wheel-side attachment section. a first backing plate material is attached to cover the entire width of the main arm, giving the first location a box-shaped cross section; a second backing plate material is attached to a second location of the main arm that is closer to the center of the main arm from the first vehicle body mounting portion, giving the second location a box-shaped cross section; a third backing plate material is attached to at least a portion of the sub-arm, giving the entire width of the sub-arm, giving the at least a portion a box-shaped cross section; and a support portion is further provided that connects the first backing plate material, the second backing plate material, and the third backing plate material. [Effects of the Invention]

[0010] The suspension lower arm of the present invention is connected to the vehicle body via each vehicle body mounting portion and to the wheel via a ball joint at the wheel-side mounting portion. The wheels move up and down due to road surface irregularities and are subjected to so-called lateral loads in the left-right direction (width direction) of the vehicle body during cornering, resulting in complex bending and torsional loads acting on the suspension lower arm. While these loads act on each mounting portion, the main arm portion and the sub-arm portion have a box-shaped cross-section due to the backing plate attached to their respective mounting portions, thereby suppressing deformation. This increases the overall rigidity. Furthermore, the backing plate is attached to reinforce areas prone to deformation, while no backing plate or equivalent member is provided in other areas, thereby reducing the overall weight of the suspension lower arm. Furthermore, if the backing plate is attached by welding, the number of locations where the backing plate is to be attached is limited, thereby reducing the number of welding locations. As a result, the number of steps required to manufacture the suspension lower arm can be reduced, and deformation and residual stress due to welding can be avoided or suppressed. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view of a suspension lower arm according to the present invention, as viewed from the bottom side. FIG. [Figure 2] 2 is a cross-sectional view schematically showing cross-sectional shapes at three points along line XX in FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0012] Next, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the embodiment described below is merely an example of how the present invention can be implemented, and is not intended to limit the present invention.

[0013] Figure 1 shows a suspension lower arm (hereinafter simply referred to as lower arm) 1 according to one embodiment of the present invention. The example shown here is what can be called an L-shaped lower arm, and Figure 1 shows the lower arm as seen from the side that becomes the underside when mounted on a vehicle (i.e., the back side). A wheel-side mounting section 3 for mounting a ball joint (not shown) for connecting to a wheel is provided at one end of a main arm section 2, which is a main body section of a predetermined width that is curved in an L-shape or arc shape. This wheel-side mounting section 3 is a cylindrical section that penetrates the main arm section 2 in the plate thickness direction, with an inner diameter slightly smaller than the width of the main arm section 2 and an edge that rises downward.

[0014] A vehicle body side mounting portion 4 for connection to a vehicle body (not shown) is provided at the other end of the main arm portion 2. This vehicle body side mounting portion 4 corresponds to the first vehicle body mounting portion in the embodiment of the present invention, and like the wheel side mounting portion 3 described above, this vehicle body side mounting portion 4 is a cylindrical portion that penetrates the main arm portion 2 in the plate thickness direction, with an inner diameter slightly smaller than the width of the main arm portion 2 and an edge that rises on the lower surface side. The lower arm 1 is connected to the vehicle body via a bushing (not shown) fitted into this vehicle body side mounting portion 4.

[0015] A branched portion (hereinafter referred to as a sub-arm portion) 5 branches off from the main arm portion 2 midway between the wheel-side mounting portion 3 and the vehicle body-side mounting portion 4, protruding in the opposite direction from the wheel-side mounting portion 3 (or toward the vehicle body-side mounting portion 4) and is formed integrally with the main arm portion 2. The sub-arm portion 5 has a shape that gradually narrows in width from the main arm portion 2 side toward the tip, and is provided at its tip with a vehicle body-side mounting portion 6 for connection to the vehicle body. The vehicle body-side mounting portion 6 corresponds to the second vehicle body mounting portion in the embodiment of the present invention, and in the example shown in FIG. 1, is configured as a cylindrical portion that faces approximately horizontally when mounted on the vehicle. The lower arm 1 is connected to the vehicle body via a bushing (not shown) fitted into the vehicle body-side mounting portion 6.

[0016] The main arm section 2 and sub-arm section 5, including the vehicle body side mounting sections 4 and 6, are pressed products made by pressing metal plate, and the edges around almost the entire periphery are bent downward at right angles to form low side wall sections 7, as shown schematically in Figure 2. The second vehicle body side mounting section 6 is formed by welding a cylindrical member to the tip of the sub-arm section 5. Furthermore, the flat surface of the main arm section 2 is formed with holes to reduce weight and mounting holes for connecting suspension members (not shown), such as shock absorbers.

[0017] Portions of the main arm section 2 that are close to the wheel-side mounting section 3 and portions that are close to the vehicle body-side mounting section 4, and at least a portion of the sub-arm section 5 (specifically, the portion that branches off from the main arm section 2) are reinforced with backing plates. First, a first backing plate 8a is provided on the main arm section 2 at a location closer to the center of the main arm section 2 than the wheel-side mounting section 3 (or a location closer to the vehicle body-side mounting section 4: a first location). This backing plate 8a is a metal plate that covers the main arm section 2 across its width, and as shown in FIG. 2 as a cross section taken along line XX in FIG. 1, is a member that has a U-shaped cross section with both ends in the width direction bent to one side (the bottom side in FIG. 2), and is joined to the main arm section 2 by welding, with both bent ends hooked onto side wall sections 7 of the main arm section 2. Of the two ends hooked onto the side wall 7, the side end on the outer periphery of the curved main arm 2 is shorter, and the side end on the inner periphery of the main arm 2 is longer. Therefore, the portion of the main arm 2 close to the wheel-side mounting portion 3 is restrained by the first back plate material 8a, and the overall shape of this portion has a box-like cross section.

[0018] Furthermore, a second back plate material 8b is provided on the main arm section 2 at a location closer to the center of the main arm section 2 than the vehicle body-side mounting section 4 (or at a location closer to the wheel-side mounting section 3: a second location). This back plate material 8b is a metal plate that covers the main arm section 2 across the width direction, and as shown in FIG. 2 as a cross section taken along line XX in FIG. 1, is a member with both ends in the width direction bent to one side (to the bottom side in FIG. 2) to form a U-shaped cross section, and the bent ends are joined to the main arm section 2 by welding in a state where they are hooked onto side wall sections 7 of the main arm section 2. Therefore, the portion of the main arm section 2 that is close to the vehicle body-side mounting section 4 is restrained by the second back plate material 8b, and the overall shape of this portion has a box-like cross section.

[0019] Furthermore, a third back plate material 8c is provided at a portion of the sub-arm unit 5 that branches off from the main arm unit 2. That is, this third back plate material 8c is intended to reinforce the sub-arm unit 5, and is attached to the base end (root portion) of the sub-arm unit 5 where bending stress is large. Specifically, the third back plate material 8c is a metal plate that covers the bottom side of the root portion of the sub-arm unit 5 that branches off from the main arm unit 2 across the width direction, and as shown in FIG. 2 as a cross section along line XX in FIG. 1, the third back plate material 8c is a member that has a U-shaped cross section with both ends in the width direction bent to one side (the bottom side in FIG. 2), and the bent ends are joined to the main arm unit 2 by welding in a state where they are hooked onto the side wall portion 7 of the main arm unit 2. Therefore, the root portion of the sub-arm unit 5 is restrained by the third back plate material 8c, and the overall shape of this portion has a box-shaped cross section.

[0020] The back plate materials 8a, 8b, and 8c are not separate but are connected and integrated by support units 9. That is, support units 9 connect the back plate materials 8a, 8b, and 8c in their planar directions (directions parallel to the underside of the main arm unit 2). Therefore, back plate materials 8a, 8b, and 8c are essentially connected to the main arm unit 2 at three locations, providing reinforcement against bending and twisting of the main arm unit 2. Of the support units 9, the portions connecting the first back plate material 8a and the second back plate material 8b and the portions connecting the third back plate material 8c and the second back plate material 8b are shaped like thin plates, while the portions connecting the first back plate material 8a and the third back plate material 8c are shaped like wide plates. In short, support units 9 are shaped so as not to protrude from the main arm unit 2 in its width direction and have a predetermined strength.

[0021] The lower arm 1 also experiences complex bending and torsional loads due to the up-and-down movement and steering of the wheels. However, the so-called main portions, i.e., the portions near the wheel-side mounting portion 3 and the portions near the first vehicle-body mounting portion 4, are reinforced with backing plates 8a and 8b to have a box-shaped cross section, thereby suppressing deformation and displacement of the wheel-side mounting portion 3 and the first vehicle-body mounting portion 4. Similarly, the sub-arm portion 5 extending from the main arm portion 2 is reinforced with a third backing plate 8c to have a box-shaped cross section, thereby suppressing deformation or displacement of the sub-arm portion 5 or the second vehicle-body mounting portion 6 at its tip. Other portions experience little stress when a load is applied, so deformation is minimal. In other words, the overall rigidity of the main arm portion 2 and the sub-arm portion 5 can be adjusted to match the rigidity of the portions that are less likely to deform when a load is applied, and the portions that are more likely to deform due to high stress can be reinforced with backing plates 8a, 8b, and 8c as described above. Therefore, the amount of backing plate materials 8a, 8b, and 8c used for reinforcement can be minimized, thereby reducing the overall weight of the lower arm 1 without compromising the rigidity or strength. Furthermore, since fewer backing plate materials 8a, 8b, and 8c are required for reinforcement, the number of welding points can also be reduced, resulting in a reduction in the number of work steps and avoiding or suppressing deformation and residual stress due to welding.

[0022] The present invention is not limited to the above-described embodiment, and the shape of the lower arm may be modified as appropriate within the scope of the object of the present invention. Furthermore, the reinforcing backing plate may have a shape other than that shown in FIG. 1 , as long as it is attached to the necessary locations of the main arm section and the sub-arm section. Furthermore, the wheel-side mounting section and the first vehicle body-side mounting section may be formed separately from the main arm section and integrated with the main arm section by welding or a predetermined bracket. Furthermore, the above-described configuration may be inverted, and the backing plate may be provided on the upper surface of the lower arm. [Explanation of symbols]

[0023] 1 Lower Arm 2 Main arm 3 Wheel side mounting part 4,6 Vehicle body side mounting part 5 Sub-arm 7 Side wall 8a,8b,8c Back plate material 9. Support Department

Claims

[Claim 1] a suspension lower arm, comprising: a main arm section curved in an arc shape or an L shape, one end of which is provided with a wheel side attachment section for attaching a ball joint; a second vehicle body attachment section for coupling to a vehicle body, the other end of which is provided with a sub-arm section branching off from a portion of the main arm section between the wheel side attachment section and the first vehicle body attachment section; and a second vehicle body attachment section for coupling to the vehicle body, at a tip end of the sub-arm section, a first backing plate member that covers the entire main arm section in a width direction is attached to a first location of the main arm section that is closer to a center of the main arm section from the wheel-side mounting portion, so that the first location has a box-shaped cross section; a second backing plate member that covers the main arm section across a width direction thereof is attached to a second location of the main arm section that is closer to a center of the main arm section than the first vehicle body mounting portion, so that the second location has a box-shaped cross section; a third back plate member that covers the entire width of the sub-arm portion is attached to at least a portion of the sub-arm portion, and the at least a portion has a box-shaped cross section; A support portion is further provided to connect the first backing plate material to the second backing plate material and the third backing plate material. A suspension lower arm characterized by:

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